The present invention relates to lighting. More specifically, the present invention relates to a compact optic lens for a high intensity light source.
The era of the Edison vacuum light bulb will be coming to an end soon. In many countries and in many states, common incandescent bulbs are becoming illegal, and more efficient lighting sources are being mandated. Some of the alternative light sources currently include fluorescent tubes, halogen, and light emitting diodes (LEDs). Despite the availability and improved efficiencies of these other options, many people have still been reluctant to switch to these alternative light sources.
There are several key reasons why consumers have been slow to adopt the newer technologies. One such reason is the use of toxic substances in the lighting sources. As an example, fluorescent lighting sources typically rely upon mercury in a vapor form to produce light. Because the mercury vapor is considered a hazardous material, spent lamps cannot simply be disposed of at the curbside but must be transported to designated hazardous waste disposal sites. Additionally, some fluorescent tube manufacturers go so far as to instruct the consumer to avoid using the bulb in more sensitive areas of the house such as in bedrooms, kitchens, and the like.
The inventors of the present invention also believe that another reason for the slow adoption of alternative lighting sources is the low performance compared to the incandescent light bulb. As an example, fluorescent lighting sources often rely on a separate starter or ballast mechanism to initiate the illumination. Because of this, fluorescent lights sometimes do not turn on “instantaneously” as consumers expect and demand. Further, fluorescent lights typically do not immediately provide light at full brightness, but typically ramp up to full brightness within an amount of time (e.g., 30 seconds). Further, most fluorescent lights are fragile, are not capable of dimming, have ballast transformers that can emit annoying audible noise, and can fail in a shortened period of time if cycled on and off frequently. Because of this, fluorescent lights do not have the performance consumers require.
Another type of alternative lighting source more recently introduced relies on the use of light emitting diodes (LEDs). LEDs have advantages over fluorescent lights including the robustness and reliability inherent in solid state devices, the lack of toxic chemicals that can be released during accidental breakage or disposal, instant-on capabilities, dimmability, and the lack of audible noise. The inventors of the present invention believe, however, that current LED lighting sources themselves have significant drawbacks that cause consumers to be reluctant to using them.
A key drawback with current LED lighting sources is that the light output (e.g., lumens) is relatively low. Although current LED lighting sources draw a significantly lower amount of power than their incandescent equivalents (e.g., 5-10 watts v. 50 watts), they are believed to be far too dim to be used as primary lighting sources. As an example, a typical 5 watt LED lamp in the MR16 form factor may provide 200-300 lumens, whereas a typical 50 watt incandescent bulb in the same form factor may provide 700-1000 lumens. As a result, current LEDs are often used only for exterior accent lighting, closets, basements, sheds or other small spaces.
Another drawback with current LED lighting sources includes an upfront cost that is often shockingly high to consumers. For example, for floodlights, a current 30 watt equivalent LED bulb may retail for over $60, whereas a typical incandescent floodlight may retail for $12. Although the consumer may rationally “make up the difference” over the lifetime of the LED by the LED consuming less power, the inventors believe the significantly higher prices greatly suppress consumer demand. Because of this, current LED lighting sources do not have the price or performance that consumers expect and demand.
Additional drawbacks with current LED lighting sources include that they have many parts and are labor intensive to produce. As an example, one manufacturer of an MR16 LED lighting source utilizes over 14 components (excluding electronic chips), and another manufacturer of an MR 16 LED lighting source utilizes over 60 components. The inventors of the present invention believe that these manufacturing and testing processes are more complicated and more time consuming, compared to manufacturing and testing of a LED device with fewer parts and using a more modular manufacturing process.
Additional drawbacks with current LED lighting sources are that the output performance is limited by the heat sink volume. More specifically, the inventors believe that for replacement LED light sources, such as MR16 light sources, current heat sinks are incapable of dissipating much of the heat generated by the LEDs under natural convection. In many applications, the LED lamps are placed into an enclosure such as a recessed ceiling that already experiences ambient air temperatures over 50 degrees C. At such temperatures the emissivity of surfaces plays only a small role in dissipating the heat. Furthermore, because conventional electronic assembly techniques and LED reliability factors limit PCB board temperatures to about 85 degrees C., the power output of the LEDs is also greatly constrained. At higher temperatures, radiation can play a much more important role, and as a result high emissivity heat sink surfaces are desirable.
Traditionally, light output from LED lighting sources has been enhanced simply by increasing the number of LEDs, which has led to increased device costs, and increased device size. Additionally, such lights have had limited beam angles and limited outputs due to limitations on the dimensions of reflectors and other optics.
Embodiments of the present disclosure use certain lighting-related terms, which are now defined.
Beam light angle refers to the angle where light intensity of a light source drops to about 50% of the maximum intensity. For example, a light source with a maximum or central beam intensity of 2000 candle power will have a beam angle defined by where the light intensity drops to about 1000 candle power.
Field angle refers to the angle where the light intensity of the light source drops to about 10% of the maximum or central beam intensity. For example, a light source with a maximum or central beam intensity of 2000 candle power will have an associated field angle within which the light intensity drops to about 200 candle power.
Direct glare associated with a light source refers to light provided by a light source within a region outside the field angle or outside 30 degrees off-axis, that is brighter than a specified percentage of the maximum output of the light source (e.g., about 0.1%). In the prior art, light output from the central portion of reflective lenses has been proposed in a variety of ways that did not provide acceptable results. For example, in U.S. Pat. No. 5,757,557 and in U.S. Pat. No. 6,896,381, the reflective lens includes a centrally located transmissive lens that disperses light directly from the high intensity center region of a light source. Drawbacks with such approaches include that the reflected light from the reflective portion of the lens and the directly transmitted light from the central portion of the lens produce two distinct light beams. When the two different light beams do not overlap, a dark gap is apparent and the output light is also undesirably non-uniform. When the two different light beams overlap, a hot spot is apparent and the output light is also undesirably non-uniform. These solutions also do not contemplate glare and do not even ways to reduce glare.
In another prior art example, U.S. Pat. No. 8,238,050, the reflective lens includes a central reflector that reflects high intensity light back to a main reflector. The main reflector then reflects the light outward from the cap. Drawbacks with such approaches include that the deliberately reflected light may not be constrained such that the light output is undesirably non-uniform. In other examples, such as disclosed in U.S. Pat. No. 6,896,381, and in U.S. Pat. No. 6,473,554, the front lens is configured to not require a central reflector. The same drawback exists with this approach because reflected light from a central region is of high intensity and contrasts with the absence of directly transmitted light from the central region. As a result, the light output is undesirably non-uniform. Additionally, these solutions do not contemplate glare and do not address ways to reduce glare.In other prior art examples, methods for reducing glare have included recessing a light source deep within a cylindrical or conical collar. Such solutions physically reduce glare by reducing the beam angle and/or field angle, similar to “barn doors” used in stage lighting. Drawbacks to such approaches include that the lighting assembly requires a deep recess housing. Such solutions cannot fit within standardized lighting physical formats and thus are not suitable for the intended purposes of a compact light source.
Accordingly, what is desired is a highly efficient lighting source without the drawbacks described above.